This invention relates to a dispenser for dispensing liquid substances or substances in the form of cream or paste, the dispenser comprising a bottle for containing said substance to be dispensed, a pump operable manually to dispense a predetermined Quantity of substance, and a socket ring for fixing the pump to the bottle mouth.
Dispensers of this type have been known for some time. The pumps used in such dispensers consist substantially of: an overall cylindrical body open at its two ends, at a first end there being provided a non-return valve: an overall cylindrical hollow shaft coaxial to the hollow body and partly enclosed in it, one end of said shaft projecting to the outside through the second end of the hollow body, the shaft being movable axially in both directions relative to the hollow body,the projecting end of the shaft carrying a dispensing knob provided with a dispensing nozzle which communicates with the interior of the shaft, the other end of the shaft comprising at least one aperture for communication between the interior of the shaft and the interior of the hollow body: a piston movable in both directions under fluid-tight conditions within the hollow body, that internal part of the hollow body situated between the piston and said non-return valve defining a pressure chamber, the piston being mounted on said shaft and being movable in both directions under fluid-tight conditions relative to the shaft to open or close said apertures in the shaft; a first helical metal return spring for returning the piston to its rest position in which the apertures in the shaft are closed when no pressure is exerted on the dispensing knob; a second helical metal return spring for returning the shaft into the position in which it most projects from the hollow body when pressure on the dispensing knob ceases; an annular closure element for the second end of the hollow body, this closure element also acting as a guide for the shaft; and connection means, provided within the pump, for connecting the bottle interior to the outside, this connection being precluded when the piston is in its rest position.
The non-return valve is normally of the metal ball type and prevents the substance to be dispensed present in the pressure chamber from returning to the bottle.
A first drawback of these known dispensers is the fact that the relative pumps contain metal parts (in particular said non-return ball valve and the first return spring) which come into contact with the substance to be dispensed, with which they could react chemically, contaminating it. As a consequence, there is also corrosion of said metal parts, which can prejudice the proper operation of the pump.
Pumps are also known in which the metal ball non-return valve is replaced by a plastics valve of particular form (see for example patent application EP-A-0469368. Specifically, these valves can be constructed of a plastics material which is not attacked by the substance contained in the bottle. This however is not sufficient to completely overcome the problem of contamination.